Very clear and helpful diagrams RVDT.
Whilst they highlight the effects of spillage through the overflow, and address the consequences of different pitch fore and aft, they are silent on the consequences of lateral pitch. It seem just as obvious that fuel would still "spill" back into the main tank, but not necessarily at the same rate for each supply tank, depending on the angle and duration of bank. The transfer pumps can only supply fuel equally to the supply tanks, so assymetrical fuel spillage will only be remedied when there is sufficient fuel in the main tank to more than fill the supply tanks. As the equal flow from the transfer pumps fills the tanks, the one with more fuel will be filled first, and the excess will overflow back to the main tank, and so on until both tanks are full. Not so easy when total fuel is at or below supply tank capacity, and of course not possible with the transfer pumps off. With the transfer pumps off, there must exist the possibility for there to be a flight profile which results in the supply tanks holding close to the same volume of fuel as opposed to the designed-in difference.
Were such a situation to arise, engine flameouts could be much closer together than expected...